1. Field of the Invention
The present invention relates to a panel.
2. Description of the Related Art
As body panels of transport machines such as automobiles, aircraft, vehicles, and ships, there generally are used panel structures each comprising an exterior trim panel (outer panel or outer exposed panel) and an interior trim panel (inner panel or inner exposed panel) both combined together. For example, for automobile hood, doors and roof there are used panel structures each comprising a relatively thin outer panel for appearance and an inner panel for reinforcing the outer panel, both panels being combined together.
These panel structures are required to exhibit a noise insulating performance and a vibration damping performance in addition to such strength and rigidity as are inherently required as structures of transport machines and the like. For example, for the hood of an automobile or the like it is required to exhibit such a noise insulating effect as diminishes a wind noise of the automobile body and an engine noise generated within the body and thereby makes the travel of the automobile comfortable. For example, in common to transport machines such as automobiles, engine noises consist mainly of noises (especially booming noises) of low frequency band not higher than 1 kHz. Therefore, panel structures for transport machines and the like are required to diminish such noises.
However, as to a conventional panel structure comprising an inner panel and an outer panel combined together by fitting or mechanically and a conventional panel structure of the type in which protuberances of an inner panel and a surface of an outer panel are bonded together merely through an adhesive, it is impossible to so much expect an insulating effect against noises of the foregoing low frequency band.
This is because the conventional panel structures are expected to exhibit only an adhesive effect (bonding effect) and therefore the inner panel having protuberances is applied with an adhesive on only the tops of the protuberances, in other words, on only a quite limited area of the panel area.
On the other hand, vibration damping steel and aluminum panels are used for noise insulation and vibration damping. These damping panels are basically of a structure in which a resin layer is formed between two panels. The resin layer is effective in displaying a sound insulating performance and a vibration damping performance. In each of the vibration damping panels it is possible to provide the resin layer throughout the whole surface of the panel and at a required thickness and hence possible to ensure an amount of resin necessary for insulating noises of the foregoing low frequency band and damping vibrations.
However, for panels for transport machines such as automobiles there are performed press forming works involving strict forming conditions such as deep drawing, bulging, bending, and stretch flanging in order to make a blank into a complicated product shape. Therefore, a blank such as a steel or Al alloy plate, even in the form of a single plate, is required to possess a high deep drawability and a high shape fixability. But the foregoing laminated vibration damping panels do not possess such a high formability as that of a single blank and are thus not employable as panels for transport machines.
In the vibration damping panel, resin is filled between two panels throughout the whole panel surfaces, so that the damping panel becomes heavier than the aforesaid panel structure by an increased amount of resin resulting from the whole-surface filling of the resin. Consequently, a problem is encountered such that the meaning of using the panel structure for the reduction in weight of a transport machine is lost.